<p dir="ltr">As the demand for energy rises and the threat of climate change looms, the need for clean, reliable, and affordable energy solutions like renewable energies has been more crucial. Energy storage systems (ESSs) are indispensable in addressing the intermittent nature of renewable energies and optimizing grid efficiency. Redox flow batteries (RFBs), thanks to their scalability, independent energy and power, swift response time, and minimal environmental impact, are a particularly promising ESS technology for long-duration storage applications. Despite the technological maturity of aqueous RFBs, nonaqueous organic RFBs (NAORFBs) are a prospective solution due to their wider operational voltage, potentially higher energy density, and larger pool of redox-active materials. However, the current state-of-the-art NAORFBs face challenges due to the lack of suitable organic redox-active materials (ORMs).</p><p dir="ltr">Despite the development of new materials, how their variables influence the total system cost of RFBs remains an unsolved challenge. With this regard, we established a techno-economic (TE) model to calculate the capital cost of nonaqueous hybrid RFBs (NAHRFBs). Prior to this work, NAHRFBs, which employs lithium metal as the anode, were regarded as an RFB system with the highest energy density. However, the correlation between their features and the system cost remained unclear, leaving a research gap for new ORMs. In our model, we selected a state-of-the-art NAHRFB system where 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) serves as the catholyte and lithium metal functions as the anode. Thereafter, sensitivity analyses identified several key factors that determine the system cost, including operational current density, area-specific resistance, cell voltage, electrolyte composition, and both the price and equivalent molecular weight of the ORM. To enhance the cost-competitiveness of current NAHRFBs, it is advised to increase the current density by 10 times and modulate the ORM-related characteristics. The virtually optimized condition manifests that the system cost of NAHRFB can meet the long-term cost target set by the U. S. Department of Energy.</p><p dir="ltr">Informed by the TE model, we discovered that elevating the oxidation potential of catholyte ORMs is instrumental in reducing the system cost of RFBs. To explore this possibility, we incorporated fluorine atoms, a potent electron-withdrawing group (EWG), into a dimethoxybenzene (DMB) derivative, yielding a new ORM (ANL-C46) with an oxidation potential enhanced by ~0.41 V. Surprisingly, ANL-C46 demonstrated superior kinetic and electrochemical stability compared to its parent molecule, as indicated by electron paramagnetic resonance (EPR) study and bulk electrolysis. In particular, the cycling performance of ANL-46 during the bulk electrolysis outperformed most reported high-potential (> 1 V vs. Ag/Ag⁺) ORMs. Density functional theory (DFT) calculations reveals that the introduced fluorine substituents suppress the typical side reaction pathways of the DMB series. These findings offer valuable insights into molecular engineering strategies that concurrently improve multiple desired ORM properties.</p><p dir="ltr">The stability of ORMs is critical for ensuring the extended lifetime of RFBs. We conducted a systematic exploration of the conjugation effect, which potentially stabilizes the ORMs by facilitating a more homogeneous distribution of delocalized charges. This was applied to tailor the electrochemical and physical properties of several DMB derivatives with varying aromatic ring counts. As we extended the aromatic core from 1,4-dimethoxybenzene (1,4-DMB) to 1,4-dimethoxynaphthalene (1,4-DMN), we noted a decrease in oxidation potential, enhanced kinetic stability, and an extended cycling life. However, further extending the aromatic core to 2-ethyl-9,10-dimethyanthracene (EDMA) results in rapid dealkylation of the radical cation due to increased strain in the methoxy substituents. Additionally, 1,4-DMN shows cross-reactions between radical cations, likely via disproportionation. This study demonstrates that extending the π-conjugation changes reactivity in multiple ways. Therefore, attempts to lower oxidation potential and improve ORMs stability through π-conjugation should be pursued with caution.</p>

Due to Vietnam’s economic development its energy demand will continue to rise by 12–16% annually over the next few years. The government has realized that supply problems in the energy sector pose a significant threat to further development. Therefore, it is making concerted efforts to modernize the existing energy sector and expand the generating structure. There are ambitious expansion plans in the field of renewable energy sources, too. Owing to its very high potential, biomass could play a key role in energy production. This paper attempts to analyze the current status of biomass based energy production in Vietnam addressing variety of aspects such as biomass potential, legal framework as well as financial aspect. Section 4 contains an overview of ongoing bioenergy projects. Instead of providing a complete picture, these examples are intended to illustrate the various ways in which biomass can be used in different economic sectors. Finally existing barriers as well as action to incentivise bioenergy are discussed. / Do phát triển kinh tế, nhu cầu năng lượng của Việt Nam sẽ tiếp tục tăng 12-16% mỗi năm trong vài năm tới. Chính phủ đã nhận ra rằng vấn đề cung cấp trong lĩnh vực năng lượng gây ra một mối đe dọa đáng kể cho sự phát triển tiếp theo. Vì vậy, có các nỗ lực để hiện đại hóa ngành năng lượng hiện có và mở rộng cấu trúc sản sinh năng lượng. Cũng có những kế hoạch mở rộng đầy tham vọng trong lĩnh vự nguồn năng lượng tái tạo. Do có tiềm năng rất cao, sinh khối có thể đóng một vai trò quan trọng trong sản xuất năng lượng. Bài viết này cố gắng phân tích tình trạng hiện tại của sản xuất năng lượng sinh khối tại Việt Nam giải quyết nhiều khía cạnh nhưtiềm năng sinh khối, khuôn khổ pháp lý cũng như các khía cạnh về tài chính. Tổng quan về các dự án năng lượng sinh học đang diễn ra được trình bày trong phần 4. Thay vì cung cấp một bức tranh hoàn chỉnh, các ví dụ được dùng để minh họa cho những cách khác nhau, trong đó sinh khối có thể được sử dụng trong các lĩnh vực kinh tế khác nhau. Rào cản cuối cùng hiện tại cũng nhưhành động để khuyến khích năng lượng sinh học sẽ được thảo luận.

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<p>  </p> <p>  </p> <p>Concentrator photovoltaics have demonstrated greater solar energy production efficiency than previous solar electric technologies.  However, recent research reveals that heat management is a significant difficulty in CPV systems, and if left unaddressed, it can have a severe influence on system efficiency and lifetime. Traditional CPV cooling relies on active methods such as forced air convection, or liquid cooling, which might lead to an extremely large parasitic power use. In addition, the moving parts of a cooling system result in a shorter lifespan and higher maintenance expenses. </p> <p><br></p> <p>CPV systems can boost their efficiency and lifespan by adopting passive cooling solutions. This work employed radiative cooling and natural convection to construct an efficient and cost-effective cooling system. The excess heat of a solar cell can be dispersed into space via electromagnetic waves via radiative cooling. Due to the fact that the radiative cooling power is related to the difference between the fourth powers of the solar cell and the ambient temperature, much greater cooling powers can be obtained at higher temperatures. Heat pipes were installed to act as a heat pump by transferring excessive heat from solar cells within a system to the exterior, where it can be dissipated via natural air cooling and thermal radiation. Experiments conducted in this study demonstrate that a temperature reduction of 21 ◦C was accomplished through radiative cooling and natural convection, resulting in an increase of 64 mV, or 17% in the open-circuit voltage of a GaSb solar cell.</p>

<p>In this research, a Split-Shaft Wind Energy Conversion System (SS-WECS) is investigated</p> <p>to improve the performance and cost of the system and reduce the wind power</p> <p>uncertainty influences on the power grid. This system utilizes a lightweight Hydraulic Transmission</p> <p>System (HTS) instead of the traditional gearbox and uses a Doubly-Fed Induction</p> <p>Generator (DFIG) instead of a synchronous generator. This type of wind turbine provides</p> <p>several benefits, including decoupling the shaft speed controls at the turbine and the generator.</p> <p>Hence, maintaining the generator’s frequency and seeking maximum power point</p> <p>can be accomplished independently. The frequency control relies on the mechanical torque</p> <p>adjustment on the hydraulic motor that is coupled with the generator. This research provides</p> <p>modeling of an SS-WECS to show its dependence on mechanical torque and a control</p> <p>technique to realize the mechanical torque adjustments utilizing a Doubly-Fed Induction</p> <p>Generator (DFIG). To this end, a vector control technique is employed, and the generator</p> <p>electrical torque is controlled to adjust the frequency while the wind turbine dynamics</p> <p>influence the system operation. The results demonstrate that the generator’s frequency is</p> <p>maintained under any wind speed experienced at the turbine.</p> <p>Next, to reduce the size of power converters required for controlling DFIG, this research</p> <p>introduces a control technique that allows achieving MPPT in a narrow window of generator</p> <p>speed in an SS-WECS. Consequently, the size of the power converters is reduced</p> <p>significantly. The proposed configuration is investigated by analytical calculations and simulations</p> <p>to demonstrate the reduced size of the converter and dynamic performance of the</p> <p>power generation. Furthermore, a new configuration is proposed to eliminate the Grid-</p> <p>Side Converter (GSC). This configuration employs only a reduced-size Rotor-Side Converter</p> <p>(RSC) in tandem with a supercapacitor. This is accomplished by employing the hydraulic</p> <p>transmission system (HTS) as a continuously variable and shaft decoupling transmission</p> <p>unit. In this configuration, the speed of the DFIG is controlled by the RSC to regulate the</p> <p>supercapacitor voltage without GSC. The proposed system is investigated and simulated in</p> <p>MATLAB Simulink at various wind speeds to validate the results.</p> <p>Next, to reduce the wind power uncertainty, this research introduces an SS-WECS where the system’s inertia is adjusted to store the energy. Accordingly, a flywheel is mechanically</p> <p>coupled with the rotor of the DFIG. Employing the HTS in such a configuration allows the</p> <p>turbine controller to track the point of maximum power (MPPT) while the generator controller</p> <p>can adjust the generator speed. As a result, the flywheel, which is directly connected</p> <p>to the shaft of the generator, can be charged and discharged by controlling the generator</p> <p>speed. In this process, the flywheel energy can be used to modify the electric power generation</p> <p>of the generator on-demand. This improves the quality of injected power to the</p> <p>grid. Furthermore, the structure of the flywheel energy storage is simplified by removing</p> <p>its dedicated motor/generator and the power electronics driver. Two separate supervisory</p> <p>controllers are developed using fuzzy logic regulators to generate a real-time output power</p> <p>reference. Furthermore, small-signal models are developed to analyze and improve the MPPT</p> <p>controller. Extensive simulation results demonstrate the feasibility of such a system and its</p> <p>improved quality of power generation.</p> <p>Next, an integrated Hybrid Energy Storage System (HESS) is developed to support the</p> <p>new DFIG excitation system in the SS-WECS. The goal is to improve the power quality</p> <p>while significantly reducing the generator excitation power rating and component counts.</p> <p>Therefore, the rotor excitation circuit is modified to add the storage to its DC link directly.</p> <p>In this configuration, the output power fluctuation is attenuated solely by utilizing the RSC,</p> <p>making it self-sufficient from the grid connection. The storage characteristics are identified</p> <p>based on several system design parameters, including the system inertia, inverter capacity,</p> <p>and energy storage capacity. The obtained power generation characteristics suggest an energy</p> <p>storage system as a mix of fast-acting types and a high energy capacity with moderate</p> <p>acting time. Then, a feedback controller is designed to maintain the charge in the storage</p> <p>within the required limits. Additionally, an adaptive model-predictive controller is developed</p> <p>to reduce power generation fluctuations. The proposed system is investigated and simulated</p> <p>in MATLAB Simulink at various wind speeds to validate the results and demonstrate the</p> <p>system’s dynamic performance. It is shown that the system’s inertia is critical to damping</p> <p>the high-frequency oscillations of the wind power fluctuations. Then, an optimization approach</p> <p>using the Response Surface Method (RSM) is conducted to minimize the annualized</p> <p>cost of the Hybrid Energy Storage System (HESS); consisting of a flywheel, supercapacitor, and battery. The goal is to smooth out the output power fluctuations by the optimal</p> <p>size of the HESS. Thus, a 1.5 MW hydraulic wind turbine is simulated, and the HESS is</p> <p>configured and optimized. The direct connection of the flywheel allows reaching a suitable</p> <p>level of smoothness at a reasonable cost. The proposed configuration is compared with the</p> <p>conventional storage, and the results demonstrate that the proposed integrated HESS can</p> <p>decrease the annualized storage cost by 71 %.</p> <p>Finally, this research investigates the effects of the reduced-size RSC on the Low Voltage</p> <p>Ride Through (LVRT) capabilities required from all wind turbines. One of the significant</p> <p>achievements of an SS-WECS is the reduced size excitation circuit. The grid side converter is</p> <p>eliminated, and the size of the rotor side converter (RSC) can be safely reduced to a fraction</p> <p>of a full-size excitation. Therefore, this low-power-rated converter operates at low voltage</p> <p>and handles the regular operation well. However, the fault conditions may expose conditions</p> <p>on the converter and push it to its limits. Therefore, four different protection circuits are</p> <p>employed, and their effects are investigated and compared to evaluate their performance.</p> <p>These four protection circuits include the active crowbar, active crowbar along a resistorinductor</p> <p>circuit (C-RL), series dynamic resistor (SDR), and new-bridge fault current limiter</p> <p>(NBFCL). The wind turbine controllers are also adapted to reduce the impact of the fault</p> <p>on the power electronic converters. One of the effective methods is to store the excess energy</p> <p>in the generator’s rotor. Finally, the proposed LVRT strategies are simulated in MATLAB</p> <p>Simulink to validate the results and demonstrate their effectiveness and functionality.</p>

<p dir="ltr">The need for reducing reliance on fossil fuels to meet ever-increasing energy demands and minimizing global climate change due to greenhouse gas emissions has led to an increase in investments in Variable Energy Resources (VREs), such as wind and solar. But due to the unreliable nature of VREs, an energy storage system must be coupled with it which drives up the investment cost.</p><p dir="ltr">Lithium-ion batteries are compact, modular, and have high cyclic efficiency, making them an ideal choice for energy storage systems. However, they are susceptible to capacity loss over the years, limiting the total life of the batteries to 15-18 years only, after which they must be safely discarded or recycled. Hence, designing a Battery Energy Storage System (BESS) should consider all aspects, such as battery life, investment cost, energy efficiency, etc.</p><p dir="ltr">Most of the available studies on cost and lifetime of BESS either consider a steady degradation rate over years, or do not account for it at all, they take constant charge/discharge cycles, and sometimes do not consider ambient temperature too. This may result in an error in estimation of the cost of energy storage. The location where the BESS is supposed to be installed can also impact its life, given that each location has its own power consumption trend and temperature profile. In this work, we attempt to simulate a BESS by considering the ambient temperature, degradation rate and energy usage. This will help in getting an insight of a more realistic estimate of levelized cost of storage and for estimating the thermal energy needed to keep them within a certain temperature range, so that they can last longer.</p>

<p dir="ltr">Counterflow diffusion flames have been studied in depth as a one-dimensional flame, and are often used to study chemical kinetics, soot formation, and extinction and ignition characteristics of flames because of the low computing costs associated with one dimensional computations. Further, strained flames have been used in models of turbulent flames with the assumption that the underlying chemistry can be represented by a limited number of variables. Detailed three dimensional simulations of H₂/CH₄/air counterflow diffusion flames are performed using CONVERGE CFD [41] and compared to one dimensional simulation and experimental Dual-Pump Coherent anti-Stokes Raman Scattering (DPCARS) measurements of temperature and normalized mole fractions of H₂ and O₂[37]. The multi-dimensional effects of differential and advective diffusion are explored. The effects of boundary conditions far from the centerline axis of the burner one flow field and flame shape are investigated.</p>

<p>The ongoing and rapidly accelerating integration of inverter-based resources (IBRs), such as solar panels, into power distribution systems has heightened the importance of computational tools that can be used to study the dynamics of such systems. IBRs use power electronics to interface the energy sources to the grid, thereby introducing faster dynamics than their electromechanical counterparts, which could lead to instabilities in distribution systems and microgrids. Hence, there is a need for conducting simulations of distribution systems containing large numbers of single- and three-phase inverters, which could be operating under either grid-following or grid-forming modes.</p> <p>A key objective of this thesis is to derive detailed, high-fidelity models of inverters and their controls in the context of unbalanced distribution networks. In addition, a diesel synchronous generator model is derived, for the sake of completeness. The main contribution of this work is that these models are developed for use in a novel simulation toolbox called Dynamic Simulation Tool using a Sparse Tableau Approach in Python, DynaSTPy (pronounced dynasty). This thesis outlines how the components can be modeled in the sparse tableau framework as electrical networks with topology described using a node-branch incidence matrix. In addition, the thesis explains how controller dynamics and constraints can be handled within this framework. These models are tailored to seamlessly integrate into the DynaSTPy toolbox. The proposed approach can be readily extended to model other such components in the future.</p>

<p dir="ltr">A three-dimensional numerical model was developed using the commercial CFD code CONVERGE to study the gas-dynamic interactions between the two chambers in a gasoline engine. The geometry and parameters of the engine used were based on a modified turbocharged GM four-cylinder 2.0 L GDI gasoline engine. Pre-chambers with nozzle diameters of 0.75 mm and 1.5 mm were used to investigate the effect of pre-chamber geometry on pre-chamber charging, combustion, and jet formation. The local developments of gas temperature and velocity were captured by adaptive mesh refinement, while the turbulence was resolved with the k-epsilon model of the Reynolds averaged Navier–Stokes (RANS) equations. The combustion process was modeled with the extended coherent flamelet model (ECFM). Data from engine experiments were compared with the computed main chamber pressures and heat release rates, and the results show good consistency with the model calculations. The scavenging and air–fuel equivalence ratio (λ) distribution of the pre-chambers improved with the larger nozzle, while the smaller nozzle generated jets with higher velocity, greater turbulence kinetic energy, and longer penetration length. Moreover, after the primary jet formation, secondary pre-chamber charging, combustion, and secondary jet formation were observed.</p><p dir="ltr">Two active PC injection strategies were designed to investigate the effect of injected hydrogen mass and PC mixture air-to-fuel equivalence ratio λ on PC combustion, jet formation, and main-chamber combustion. Stoichiometric or rich hydrogen/oxygen mixtures are actively injected into the pre-chamber to enhance the combustion processes in the pre-chamber and the main chamber. A three-dimensional numerical engine model is developed using the commercial CFD code CONVERGE. The engine geometry and parameters adopt a modified GM 4-cylinder 2.0L GDI gasoline engine. The local developments of gas temperature and velocity are resolved with the adaptive mesh refinement (AMR). The turbulence of the flow is computed with the k-epsilon model of the Reynolds averaged Navier–Stokes (RANS) equations. The turbulent combustion process is modeled with the extended coherent flamelet model (ECFM). Numerical results such as main chamber pressures and heat release rates are compared with experimental measurements, showing good consistency. Detailed analysis is performed to study the effect of the active pre-chamber injection with hydrogen on jet properties and turbulence chemistry interactions. An EGR limit of 36% was observed by injecting a stoichiometric hydrogen-oxygen mixture into the pre-chamber due to its high laminar flame speed and adiabatic flame temperature.</p>

<p dir="ltr">The chemical industry faces unprecedented pressure to reduce its carbon footprint while meeting growing global demand. As a major contributor to greenhouse gas emissions, accounting for approximately 7% of global carbon release, the sector plays a crucial role in achieving net-zero goals. This challenge is further compounded by projections suggesting that demand for chemicals could increase up to four-fold by 2050, and by the sector's role in producing several raw materials for other industries.</p><p dir="ltr">Within this context, endothermic reactors are of particular concern. The production of ethylene, propylene, and hydrogen alone accounts for around 3.6% of global CO2 emissions, representing over half of the chemical industry's total release. This situation underscores the need for alternatives in reactor design and operation.</p><p dir="ltr">To address these challenges, we introduce novel decarbonized process schemes and unit operations. The research centers around the development of Electric Reaction Towers (ERTs), a novel reactor configuration designed to ensure consistent product composition despite intense process fluctuations, such as those associated with Variable Renewable Energy (VRE). This is achieved by creating Custom Non-linear Heat Profiles (CNHPs) that maintain the key dimensionless groups of the system under dynamic conditions.</p><p dir="ltr">We present the concept of ERTs, explore their key principles, and the intuition behind their design. Additionally, we introduce Modular Reaction Towers (MRTs), which retain the benefits of handling fluctuations while addressing the investment and logistical challenges of adopting electric reactors.</p><p dir="ltr">The research employs a combination of Dimensional Analysis, Process Simulations, and Computational Fluid Dynamics (CFD) to evaluate these novel designs. Using ethylene production as a case study, we demonstrate that ERTs can enhance output by up to 4.2 times compared to state-of-the-art industrial designs.</p><p dir="ltr">The study further explores several additional concepts: Intermediate Cooling Zones (ICZs) and their potential to optimize complex reaction systems; the application of MRTs in the decentralized production of liquid hydrocarbons from shale gas to reduce flaring; and TurboQuenching, a novel approach to rapidly cool reaction products without a cooling agent while co-producing power. Finally, we discuss the broader implications of these innovations for the chemical industry's transition to more sustainable and efficient production methods.</p><p dir="ltr">By fundamentally re-thinking reactor design, this research contributes to the development of more efficient and sustainable production methods in the chemical industry, supporting the transition to a Net-Zero future.</p><p><br></p>